The present invention relates to an optical element for projection equipment and particularly a color wheel for filtering use in the projection equipment.
The commonly used projection equipment project light from a high luminous lamp. The light passes through a color wheel consisting of filters to attain a full color effect, then is projected to form an image through a lens. Color quality of the projecting image is an issue all producers have been pursuing.
The design of the color wheel directly affects the color quality of the projecting image. Refer to FIG. 1 for a conventional color wheel. It includes a circular disk carrier 1 with a bulged rim 2 and a filter set 3 with a center opening. The circular disk carrier 1 has a surface 4 coated with a layer of adhesive, then the filter set 3 is bonded to the surface 4 of the carrier 1 through coupling the center opening of the filter set 3 on the bulged rim 2 to form the color wheel. The color wheel thus formed is tested for balance to ensure reaching the required quality. However, when the adhesive is coated on the surface 4 of the carrier 1 that has the bulged rim 2 formed thereon, it is difficult to get an evenly coating, and the thickness of the coating adhesive has variations. The thickness of the color wheel also increases. As a result, the color wheel cannot attain a balanced rotation. Other means have to be adopted to improve such a situation, such as to increase or decrease the substance of the color wheel. When the improvement fails, the color wheel has to be discarded.
There are other types of color wheels. FIG. 2 shows an example disclosed in Taiwan patent No. 90212025 which is constructed to prevent spilling of the adhesive. It includes a carrier element 5 and a filter set 6. The carrier element 5 has a bonding zone with at least one annular groove 7 formed thereon. During dispensing the adhesive on the carrier element, excessive adhesive flows into the annular groove 7. While it overcomes the adhesive spilling problem, the problem of uneven adhesive coating remains unresolved.
As the conventional methods mentioned above dispense adhesive on a large area on the surface of the carrier, they are prone to create the problem of uneven coating. This problem remains to be overcome.
Therefore the primary object of the invention is to resolve the problem of uneven coating of adhesive that occurs to conventional color wheels. The invention provides a design of the color wheel that has apertures for evenly dispensing and distributing the adhesive without increasing the thickness of the color wheel.
In order to achieve the object set forth above, the color wheel having a bonding apparatus according to the invention includes a carrier and a filter set. The carrier is a circular disk and has a first surface and a second surface. The first surface has a bulged rim. A plurality of apertures are formed on the carrier between the bulged rim and the perimeter of the carrier. The filter set is mounted onto the first surface of the carrier. Adhesive is injected and filled into the apertures from the second surface such that the filter set is bonded to the first surface of the carrier to form the color wheel. By means of such a design, the adhesive may be evenly dispensed and coated without increasing the thickness of the color wheel.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.